1. Preheat oven to 350 degrees. 2. Grease and flour round bundt pan. 3. In large mixing bowl, combine butter, sugar, eggs, ricotta, oil, 3 Tbs zest, 2/3 cup juice and vanilla. 4. In small bowl combine dry ingredients. 5. Add dry ingredients to wet, blend well. 6. Add to bundt pan. Bake approx 60 mins or until done.
To make icing: 1 cup powdered sugar 5 Tbs grapefruit juice Drizzle on top of cooled cake. Garnish with remaining grapefruit zest.